Flat X-ray detectors currently have usable areas of up to 43×43 cm2. In order to manufacture these sizes, it is necessary to manufacture the basic component, the plate (which, for example, is composed of amorphous silicon) with a large area. Since machines in production are not designed for sizes such as these, it is known to join together a plurality of plates and to adhesively bond them to one another on a substrate, for example a glass substrate. This process of bonding them to one another is also referred to as butting. A large-area flat detector may include, for example, two or four individual plates. By way of example, the Pixium 4600 detector from the Trixell Company has four individual plates composed of amorphous silicon.
Since adhesive is used for the butting process, and its behavior is not ideal, this results in principle in butting structures which have defects over the entire width of the images recorded using the completed flat X-ray detector.
One particular type of defect is caused by bubbles in the adhesive used for the butting process, and by local areas in which there is no adhesive. These particular artifacts are locally limited to specific areas in the butting zone. They are distinguished by disturbing structures in the images, particularly in the case of irradiation processes from one side, which are limited to only one plate (that is to say a half-panel or quarter-panel). These local artifacts normally have a size of five or six lines or columns on each plate side. These defects can be identified by a light-and-shadow effect, normally with disturbing brightening of the image on one side of the butting zone, and darkening of the image on the other side of the butting zone.
The artifacts may be sufficiently disturbing that a flat X-ray detector which exhibits them can no longer be used, and must be assessed as scrap.
It is problematic to record the artifacts at all by measurement. Developments are known for measurement of this effect using X-ray radiation. The detector is irradiated using lead plates, which cover a plate in such a manner that they extend slightly above the butting zone. That part of the detector which is not covered is in this case subjected to direct radiation. The problem is the accuracy of the lead-plate arrangement and the reproducibility of the measurements, as well as the time taken. Furthermore, the detector must be manufactured completely, and in particular must already have a scintillator for conversion of X-ray radiation to light which can be detected by the plates.